1. Field of the Invention
The present invention relates to a recording apparatus such as a printer or a plotter, wherein marking fluid containers each formed with a ejection port (or ports) are respectively reciprocated back and forth about the ejection port by means of a driving means and intermittently stopped, so that marking fluid can be ejected from each marking fluid container through the ejection port by inertia induced in the marking fluid each time the container is stopped.
2. Description of the Prior Art
A recently spread ink-jet printing method mainly uses the DOD (Drop On Demand) process, and the DOD process has been increasingly and more widely used in the art since ink droplets can be rapidly ejected under atmospheric pressure without being electrically charged nor deflected, whereby the recording operation can be facilitated.
The typical ejection principles are the heating type ejection using resistors and the vibrating type ejection process using piezo-electric transducers.
FIG. 1 illustrates the principal of a heating type ejection process, wherein ink is contained within a chamber a1, each comprising an ejection port a2 opened toward a recording media and a resistor a3 embedded within the bottom wall of the chamber opposite to the ejection port a2 to generate heat for expanding air bubbles within the chamber a1. Therefore, expanded air bubbles will propel ink contained within the chamber a1 through the ejection port and ink droplets will be ejected toward the recording media by the propelling force.
The heating type ejection process includes various disadvantages in that ink undergoes chemical deterioration due to the applied heat and the chemically deteriorated ink deposits on the internal surface of the ink ejection port thereby causing the blocking of the ejection port. Also, the heating resistors have short life spans, and the printed documents cannot be easily recycled since water-soluable inks have to be used.
FIG. 2 illustrates the principal of a vibrating type ejection process, wherein ink is contained within a chamber b1, the chamber comprising an ejection port b2 opened toward a recording media and a piezo-electric transducer b3 embedded within the bottom wall of the chamber opposite to the ejection port b2 to generate vibration. Therefore, as the piezo-electric transducer b3 generates vibration at the bottom wall of the chamber b1, the ink will be propelled through the ejection port b2 and thus will be ejected toward the recording media by the vibration force.
The vibrating type ejection process using vibration generated by the piezo-electric transducers has an advantage that various kinds of inks can be used since it does not use heat. However, the process also entails a disadvantage in that it is difficult to form and install the transducers within the bottom wall of each chamber and thus the productivity thereof is very poor.
FIG. 3 illustrates the principal of a magnetic field applying type ejection process, wherein ink is contained within a pipe c1, magnets c2 and c3 are disposed at the upper and lower sides of the pipe c1, respectively, and an ejection port c4 is formed at one end of the pipe, and wherein electric current is applied to the ink between the magnets c2 and c3. The ink contained within the pipe is electrically charged and thus will be ejected by magnetic force generated between the magnets c2 and c3 through the ejection port c4 and toward a recording media, when electric current is applied to the ink.
The magnetic field applying type ejection process has disadvantages in that ejection ports are easily blocked by the corrosion of electrodes, power consumption is very high, and it is difficult to select magnetic materials.
The conventional printing methods as explained in the above have additional disadvantages as follows:
Printers using the above mentioned ejection processes have a resolution of about 600 DPI (dots per inch) and it is not easy to enhance the DPI more densely. Since, as can be seen from FIG. 4, the diameter d1 of chambers for supplying ink is two or more times greater than the diameter d2 of ejection ports and, particularly in the case of the heating type ejection process, heat generated from a resistor within a chamber can affect the adjacent chambers and cause malfunction, it is impossible to reduce the distances d3 between two adjacent chambers.
Furthermore, the thickness of plates d4 forming ejection ports d5 is relatively thick in printers adopting any of the. above ejection processes in order for ink droplets to arrive at. exact target points on a recording media without diffusion or deviation. However, since lengths of the ejection ports are too long, foreign matter such as cured ink and dusts easily deposits on the internal surfaces of the ejection ports and block the ejection ports after long periods of use. This problem cannot be solved by merely modifying the ingredients of the ink itself.